The invention relates to a disc brake and, in particular, to a disc brake for a utility or commercial vehicle having a brake caliper, which surrounds a brake disc and which is fastened to a positionally fixed brake carrier by two fastening elements so as to be axially movable in relation to the brake disc. The fastening elements have, in each case, one guide bar which is fixedly connected to the brake carrier. For the axial mobility of the brake caliper, one guide bar is guided in a plain bearing, which is embodied as a fixed bearing, and the other guide bar is embodied as a floating bearing.
In such disc brakes, which are used predominantly in heavy utility or commercial vehicles, the brake caliper, which is also referred to as a sliding caliper, is connected to the vehicle-mounted brake carrier by way of fastening elements. Here, guide bars engage into the brake carrier, which guide bars are guided at the other side in plain bearings of the brake caliper, so as to enable an axial movement, in relation to the brake disc, of the brake caliper with respect to the positionally fixed brake carrier.
One of the plain bearings is designed as a fixed bearing with a small amount of sliding play, while the other plain bearing functions as a floating bearing, as a result of which in particular production tolerances are compensated.
Here, it has proven to be expedient to use a guide bush in the floating bearing, which guide bush has a bearing sleeve composed of an elastomer and held in the brake caliper so as to be immovable. In addition to low production costs, a guide bush of this type is characterized by a certain degree of robustness, and simple assembly. Furthermore, operational rattling noises are prevented by the elastomer bearing sleeve.
To protect the guide bar and the sliding surfaces which are formed together with the guide bush, it is known to cover the guide bar, on its end side facing away from the brake disc, with a cap.
The guide bush itself, including the elastomer bearing sleeve, is however exposed, wherein in particular in the case of use in vehicles which are used on unsurfaced or very dirty roads, stone impacts and contamination with dirt can result in damage to the guide bush, and the entry of dirty water into the guide region. This results in increased bearing wear, which necessitates early replacement of the guide bush and possibly of the guide bar. This is naturally associated with considerable cost expenditure, not least on account of the required interruption in service of the vehicle.
The invention is therefore based on the object of further developing a disc brake such that the service life is increased, even under extreme operating conditions, with little expenditure in terms of design and production.
This and other objects are achieved according to the invention by providing a disc brake for a utility or commercial vehicle having a brake caliper, which surrounds a brake disc and which is fastened to a positionally fixed brake carrier by two fastening elements so as to be axially movable in relation to the brake disc. The fastening elements have, in each case, one guide bar which is fixedly connected to the brake carrier. For the axial mobility of the brake caliper, one guide bar is guided in a plain bearing which is embodied as a fixed bearing, and the other guide bar is guided in a plain bearing which is embodied as a floating bearing. At least the floating bearing has (i) a guide bush, which engages around the guide bar and is connected to the brake caliper so as to be immovable, (ii) an elastomer bearing sleeve, and (iii) a cap which covers the guide bar on its end side facing away from the brake disc. The cap is fastened, so as to cover the guide bush at the end side, to the elastomer bearing sleeve at least in an axial partial region at an outer side.
With little production expenditure, sealing is now obtained of the sliding region between the guide bush and the guide bar, which concomitantly encloses the elastomer guide bush. It is thus possible to refer to hermetic sealing of the plain bearing, by which operational wear, caused for example by contamination and stone impacts, can be eliminated.
This naturally leads to a reduction in operating costs of the utility vehicle which is used, since corresponding repair intervals are lengthened significantly.
Furthermore, disc brakes which are already in operation may be retrofitted with floating bearings according to the invention in the event of repairs being carried out.
According to one advantageous refinement of the invention, provision is made for the cap to be attached to the brake caliper, with the attachment region of the cap preferably being designed as an encircling, radially outwardly aligned collar, which can rest in a depression of the brake caliper.
Provision is also made for the cap to be connected in a positively locking and/or frictionally locking manner to the guide bush.
Here, the cap may bear in a frictionally locking manner against the elastomer bearing sleeve. It is however also contemplated for the cap to alternatively or additionally be connected to a metal sleeve which surrounds the elastomer bearing sleeve. The metal sleeve is also encapsulated in regions by the elastomer bearing sleeve.
The connection of the cap to the metal sleeve, which is preferably composed of steel, takes place by an interference fit, while the contact of the elastomer bearing sleeve against the cap takes place by encircling, integrally formed lips, which bear under deformation against the inner wall of the cap.
In combination with the interference fit of the metal sleeve, reliable sealing of the floating bearing is thus obtained in a simple manner by way of the cap.
Further advantageous refinements of the invention are described herein.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.